Self-locking fasteners

ABSTRACT

A self-locking screw having an elongated beam extending transversely of the screw at one end of the screw. The beam is formed from the material of the screw and has a length less than the diameter of the screw. A distal end of the beam is adapted to engage the axial wall of a generally cylindrical opening to lock the screw in place. A removal tool is also provided to remove the screw. The tool engages in a tool-engaging well in the screw and deflects the beam radially inwards to disengage the beam from the wall of the opening.

United States Patent Krywitsky et al.

[4 1 May 16, 1972 [54] SELF-LOCKING FASTENERS [72] Inventors: Leo L.Krywitsky, Toronto; Robert S. Morrow, Weston, Ontario, both of Canadaabandoned.

[52] U.S.C1 ..15l/14,151/9,151/11, 151/21,151/48,151/50,l45/50.1 [51]Int. Cl ..F16b 39/30, F16b 39/02, F16b 39/00 [58] FleldoiSearch..151/6,9,10,11,l2,13,l4, 151/21 B, 22, 24, 25, 26, 39, 40, 48, 49, 50;145/501, 52

[56] References Cited UNITED STATES PATENTS 413,580 10/1889 Talbot..151/21 B 783,088 2/1905 Vaughan... ....l51/1l 1,764,168 6/1930 Hosking....151/14 1,849,240 3/1932 McCrudden ..l51/22 1,874,389 8/1932 Trotter..151/14 1,874,657 8/1932 Trotter 151/14 1,887,616 11/1932 Berge.....l51/l4 2,019,387 10/1935 Blair 151/21 B 2,372,888 4/1945 Duggan..151/24 FOREIGN PATENTS OR APPLlCATlONS 2,645 2/1903 Great Britain..151/48 4,391 2/1912 Great Britain.... ...15l/11 204,180 9/1923 GreatBritain.... ....151/6 353,581 5/1961 Switzerland ..151/44 PrimaryExaminer-Marion Parsons, Jr. Attorney-Rogers, Bereskin & Parr 57ABSTRACT A self-1ocking screw having an elongated beam extendingtransversely of the screw at one end of the screw. The beam is formedfrom the material of the screw and has a length less than the diameterof the screw. A distal end of the beam is adapted to engage the axialwall of a generally cylindrical opening to lock the screw in place. Aremoval tool is also provided to remove the screw. The tool engages in atool-engaging well in the screw and deflects the beam radially inwardsto disengage the beam from the wall of the opening.

2 Claims, 9 Drawing Figures PATENTEDMM 16 I972 SHEET 1 [IF 2 INVENTORSLEO L. R TSKY ROBE S. ORROW PATENTEDMAY 16 I912 3, 662 804 SHEET 2 0F 2INVENTORS LEO L. KRYWITSKY ROBERT S. MORROW BY SELF-LOCKING FASTENERSThis application is a Continuation of application Ser. No. 737,685 filedon June 17, 1968, now abandoned.

This invention relates to self-locking screws and to a tool for removingthe screws.

Grub screws, locking screws and the like are commonly used to lock amachine part in place. In many cases a locking screw is simply tightenedso that it is unlikely to work loose. In other cases where the screw maybe subjected to relatively large temperature variations or mechanicalvibration the locking screw is manufactured with a peripheraldeformation such that when the screw is fed into a threaded opening in aworkpiece,there is a frictional resistance to turning which tends toprevent release of the screw. However the force required to enter thescrew is not significantly different from the force required to removeit from the opening and the screw can be removed without excessivedamage to the openlng.

It is is one of the, objects of the present invention to provide aself-locking screw which when fed into a threaded opening, requires arelatively large force to remove the screw. It is also an object toprovide a tool for removing the screw such that the screw can be removedwithout damaging the threaded opening Accordingly the invention in oneof its aspects provides a screw having an elongated beam extendingtransversely of the screw at one end of the screw. The beam is formedfrom the material of the screw and has a length less than the diameterof the screw. A root end of the beam is connected to the screw and adistal end is adapted to engage the wall of a threaded opening to lockthe screw in place. If an attempt is made to remove the screw without aspecial tool the beam acts as a strut and the distal end cuts into thematerial of the opening thereby locking the screw in the opening.

In another of its aspects the invention provides a tool for removing thescrew. The tool is adapted to engage in a toolengaging recess or well inthe screw and to deflect the beam out of locking contact with theopening.

The invention will be better understood with reference to the drawingswherein:

FIG. I is a side view of a set-screw according to the invention;

FIG. 2 is a top view of the set-screw;

FIG. 3 is a view similar to FIG. 2 showing the screw in a threadedopening;

FIG. 4 is an enlarged view of the portion of the screw;

FIG. 5 is a perspective view of another embodiment of the invention;

FIG. 6 is a perspective view of a tool for use with the invention;

FIG. 7 is a side view of the tool;

FIG. 8 is a view of the tool taken from the bottom of FIG. 7; and

FIG. 9 is a part sectional view of the tool taken from the side of FIG.7 showing the tool in use to remove a screw.

Reference is first made to FIGS. 1 and 2 with particular reference toFIG. 2. A set-screw 10 having a leading end 12 and a tool-engaging end14 has a helical thread 16 extending between the tool-engaging end 14and the leading end 12. The tool-engaging end 14 has a hexagonal recessor well 18 for receiving an Allen key to position the screw 10 in athreaded opening. A transverse elongated beam 20 is formed in thetool-engaging end 14 from the material of the screw 10 for locking thescrew in the threaded opening.

The beam 20 includes a relatively large root end 22 and a smaller distalend 24. An outer face 26 of the beam is substantially chordal withrespect to the circular periphery of the screw 10, and an inner face 28forms a portion of the wall of the well 18. The outer face 26 tapersoutwardly axially from the tool engaging end 14 for co-operating with aremoval tool as will be described. The upper face of the beam 20 is inthe plane of the tool-engaging end 14, and a lower face 30 is separatedfrom a shoulder 32 on the set-screw 10 to allow the beam 20 to flex fromthe root end 22. Because the beam 20 is formed from the material of thescrew 10, the distal end 24 is threaded so that when the screw endenters the threaded opening, the distal end follows the threads as thescrew is turned in the opening. If required, the beam can be made withmore resilience by changing its shape to conform with the chain dottedoutline of FIG. 2.

Reference is now made to FIG. 3 which shows the screw 10 in a threadedopening 34 of a workpiece 36. In manufacture the beam is machined fromthe parent metal of the screw 10 and then deformed slightly by bendingthe beam such that the distal end 24 moves radially outwards into theposition shown in FIG. 2. When the screw enters the opening 34, the beamdeflects such that the distal end 24 moves radially inwards so that thescrew can be entered into the opening with relatively little frictionalresistance. However when an attempt is made to remove the screw 10 fromthe opening 34, the beam 20 locks the screw and prevents removal. Thelocking action is caused by a leading edge 38 of the distal end 24.Because of the bending of the beam 20, the leading edge, which islongitudinally oriented in relation to the set-screw 10, digs into themetal around the opening 34. This action is better shown in FIG. 4 whichshows the leading edge 38 in contact with the opening 34 in theworkpiece 36. As seen in this figure, the leading edge 38 has both aclearance angle a and a rake angle b. Consequently when an attempt ismade to remove the screw, the edge 38 tends to remove metal from theworkpiece 36 resulting in a relatively large locking force. As furtherforce is applied to remove the screw, the beam 20 acts a strut andconsequently can resist very large turning forces applied to the screw.If the force is sufficiently large, and the material of the workpiece 36is of a material such as steel, the screw 10 will normally only beremoved after sufficient force is applied to break the beam 20.

The action of the locking beam 20 differs from that of prior devicesused to lock screws in that the beam 20 does not rely on a frictionalforce, but relies on a cutting action to lock the beam and hence thescrew in place.

If required, the locking beam 20 can be incorporated in the leading endof the screw 10 in which case the beam 20 would be a mirror image ofthat shown in FIG. 2. to allow entry of the screw 10 in the opening 34.Removal of the screw would only be possible from the tool engaging endby applying sufiicient force to break the beam 20. However if theopening 34 is accessible from both ends, the leading end can be made ina similar form to the present tool-engaging end 14 so that a removaltool can be engaged in the screw for removal of the screw. In this caseremoval will take place from an opposite end of the screw to the endused for insertion of the screw and the screw would in effect have twotool engaging ends. For the purpose of the present description however,the term toolengaging end is used to describe an end of the screw havinga locking beam and tool engaging well such as shown in FIG. 1.

Reference is now made to FIG. 5 which shows a bolt 40 having a head 42in which is formed a locking beam 44. The beam is similar in allrespects to the beam 20 (FIG. 2) but for the fact that the beam 44 isformed in the head 42 of the bolt 40. The bolt 40 is of a type which isto be recessed in a workpiece such that head 42 does not protrude fromthe workpiece. A cylindrical recess in the workpiece houses the head 42with a minimum of clearance such that the beam 44 locks the bolt 40 byengaging with the wall of the recess.

Reference is now made to FIG. 6 which illustrates a tool 46 and driver48 for removing the screw 10 from an opening such as 34 (FIG. 3). Thedriver 48 is a simple hand tool having a hexagonal recess 50 at itsleading end and a handle 52 at its outer end. Tool 46 includes an outerhexagonal bar 54 adapted to engage in the recess 50 for turning the tool46 by hand. An outer hexagonal bar 55 which may be a continuation of bar54,if required,is of a size for engaging in the well 18 (FIG. 2) of thescrew 10. The bars 54, 55 extend from respective outer and inner ends ofa cylindrical member 56 which is rigidly attached concentrically to thebar 54. The cylindrical member has a tapered extension 58 extending fromits outer end in generally parallel relationship with the bar 55. Theextension 58 however does not extend to the outer end 59 of the bar 55for reasons which will be explained. A longitudinally extending recess60 in the bar 55 extends from the cylindrical member 56 outwards for adistance slightly greater than the axial extent of the tapered extension58.

Reference is next made to FIGS. 7 and 8 which illustrate the orientationof the outer hexagonal bar 54 in relation to the tapered extention 58.As best seen in FIG. 8 an adjacent flat surface 62 on the hexagonal bar54 defines an acute angle with an inner face 63 of the extension 58, andthe bottom 57 of the recess 60 is planer as shown by the dotted line inFIG. 8, the bottom 57 of recess 60 also forms the same acute angle withthe flat surface 62 of bar 55. This angle is necessary to accommodatethe beam 20 (F162) between the bar 55 and tapered extension 58. Theangle is therefore determined by the shape of the beam 20. However,because the beam is preferably tapered from its root end 22 to itsdistal end 24, there will be an angle (measured in a transverse plane)between the flat surface 62 of bar 55 and the surface 63 of extension58. To facilitate engagement of the extension 58 and the beam 20 theface 63 of extension 58 is tapered longitudinally as is the outer face26 of beam 20 to provide a wedge action to deflect the beam 20 inwardlyas the tool is engaged with the screw. This is best seen in FIG. 9 wherethe beam 20 is shown in engagement with the extension 58. The recess 60in bar 55 permits the beam 20 to deflect radially without interferingwith the bar 55.

What we claim as our invention is:

1. In a generally cylindrical self-locking set-screw having alongitudinal axis, a leading end and a tool engaging end, the

improvement comprising: an elongated beam extending transversely of saidlongitudinal axis, said beam being formed from the material of saidscrew and said beam having a length less than the diameter of the screw,said beam being adapted to engage the wall of a threaded hole such thatsaid set-screw can be tightened relatively easily into said hole, andsuch that said set-screw resists removal from said hole, said beamcomprising: an upper face lying generally in the plane of said toolengaging end; a relatively large root end by which said beam is attachedto said tool-engaging end of said screw; a relatively small distal endwhich is normally slightly outside the cylindrical boundary of theset-screw, said distal end comprising a portion of the threads of saidset-screw and said beam being tapered from said root end to said distalend; a leading edge on said distal and extending longitudinally of saidset screw, said leading edge having clearance and rake angles so thatwhen said set-screw is in said threaded hole said leading edgeinterferes with said threaded hole to resist removal of said setscrewfrom said hole; and a generally planar outer face extending transverselyof said screw in a plane generally parallel to said longitudinal axisfor receiving a tapered extension on a removal tool whereby longitudinalforce on said tool deflects said distal end inwardly out of contact withsaid hole to allow removal of said set-screw.

2. The invention as claimed in claim 1 which further comprises: a lowerface similar to said upper face and parallel thereto; a tool-engagingwell formed in said tool-engaging end; and an inner face of said beamopposite to said outer face, said inner face forming a portion of saidtool-engaging well.

1. In a generally cylindrical self-locking set-screw having alongitudinal axis, a leading end and a tool engaging end, theimprovement comprising: an elongated beam extending transversely of saidlongitudinal axis, said beam being formed from the material of saidscrew and said beam having a length less than the diameter of the screw,said beam being adapted to engage the wall of a threaded hole such thatsaid set-screw can be tightened relatively easily intO said hole, andsuch that said set-screw resists removal from said hole, said beamcomprising: an upper face lying generally in the plane of said toolengaging end; a relatively large root end by which said beam is attachedto said tool-engaging end of said screw; a relatively small distal endwhich is normally slightly outside the cylindrical boundary of theset-screw, said distal end comprising a portion of the threads of saidset-screw and said beam being tapered from said root end to said distalend; a leading edge on said distal end extending longitudinally of saidset screw, said leading edge having clearance and rake angles so thatwhen said set-screw is in said threaded hole said leading edgeinterferes with said threaded hole to resist removal of said set-screwfrom said hole; and a generally planar outer face extending transverselyof said screw in a plane generally parallel to said longitudinal axisfor receiving a tapered extension on a removal tool whereby longitudinalforce on said tool deflects said distal end inwardly out of contact withsaid hole to allow removal of said set-screw.
 2. The invention asclaimed in claim 1 which further comprises: a lower face similar to saidupper face and parallel thereto; a tool-engaging well formed in saidtool-engaging end; and an inner face of said beam opposite to said outerface, said inner face forming a portion of said tool-engaging well.